Electroluminescence (EL) elements utilizing a substance which emits light by itself through an EL phenomenon when a voltage is applied thereto are known as a type of light emitting element which forms a display apparatus such as a display device and an illumination apparatus. The EL element is a light emitting element of thin film shape in which a light emission layer made from an organic material or an inorganic material is formed between an upper electrode and a lower electrode, and has a structure in which light emission is caused by applying a voltage to the light emission layer with the upper electrode and the lower electrode.
In recent years, development work has been underway on light emitting elements having a resonator structure (so-called microcavity structure) in which one of the upper electrode and the lower electrode is formed of a total reflection mirror and the other is formed of a semi-transmitting mirror allowing transmission of some of wavelengths, thereby resonating light emitted by the light emission layer (see, for example, Patent Documents 1 and 2).
However, the thin-film light emitting element of the resonator structure has color filter characteristics which are sensitive to an intermirror distance (resonator optical path length). For example, if nonuniformity occurs in the resonator optical path length due to manufacture errors during the manufacture process, color coordinates (color purity) and luminance variations in a front direction may be unacceptable.
The resonator structure can be designed with a relatively large margin for color purity. On the other hand, the luminances of light emitting elements for a blue (B) color and a red (R) color may vary unacceptably due to a shift of a central wavelength. For example, if the film thickness (corresponding to the optical path length) associated with the intermirror distance changes approximately 5 nm (approximately 5% of the overall element film thickness), the central wavelength may also change approximately 5 nm. For example, in the blue-color light emitting element in which the design value of the central wavelength is set to 470 nm, if the film thickness increases 5 nm, luminous efficiency at the shifted central wavelength (for example, 475 nm) changes as much as 20% or more to cause a large luminance change and thus a reduction in image quality (luminance ununiformity).